Impact of PCB Manufacturing, Design, and Material to PCB Warpage A. - PowerPoint PPT Presentation

Impact of PCB Manufacturing, Design, and Material to PCB Warpage A. Caputo 2 , S.R. Aravamudhan 2 , H. Fu 1 , N. Hubble 3 , C. Olson 3 , M. Huang 4 , A. Hsieh 4 , J.W. Cai 5 , Y. Li 5 , D. Li 5 , P. Vernhes 6 , B. Feit 6 , P.L. Toussaint 6 , CC. Chang 7 , L.L. Qin 7 , C.Y. Hsu 7 , C. Lin 8 1 iNEMI, 2 Intel Corporation, 3 Akrometrix, 4 Wistron Corporation, 5 Shengyi Technology, 6 Insidix, 7 Unimicron, 8 HannStar Board Corporation

Agenda • Project Motivation • iNEMI Project Overview • DOE set-up • Experimental set-up • Phase 1: Matching study • Results ü Phase 2: The effect of post PCB manufacturing bake on PCB warpage ü Phase 3: The effect of PCB manufacturing, thickness, and material on PCB warpage • Summary • Next steps

Project Motivation Background: • PCBs with thickness ≤ 1.0mm (40mils ) are driving higher PCB warpage in board assembly process leading to lower assembly yields and higher rework for some components • IPC-TM-650 (Bow & Twist) specification for incoming PCB warpage is not sufficient to address the warpage at elevated assembly reflow temperature Objectives of the iNEMI Project: • Guidelines/recommendation to minimize PCB warpage for thin PCBs as a function of PCB fabrication, PCB design and PCB assembly processes Value to Industry: • Reduce SMT risk for semiconductor packages (reduction in PCB warpage will provide margin to semiconductor packages) and proliferate the iNEMI project learnings to industry

iNEMI Project Overview Phase 1: Proj oject Phase Phases 2 s 2-3: PCB 3: PCB Phase Phase 4: PCB 4: PCB Phase Phase 5: A 5: Asse ssembly mbly Planning Planning Fabri rication on DOE Desi Design DOE gn DOE Proc ocess DOE PCB Fabrication DOE Project Planning PCB Design DOE PCB Assembly Process DOE • Identify PCB fabrication • Align on DOE details • Identify PCB design • Identify PCB assembly process processes impact to parameters impact to parameters impact to warpage • Identify PCB designs for warpage warpage • Focus on reflow pallet evaluation • Lamination process • CU balance across material & design elements • Identify PCB vendors to support layers • Center vs. Corner the project • Evaluate across 2 PCB • CU balance between thicknesses, 2 PCB dimension • Evaluate across 2 PCB • Evaluation and identification of thicknesses, 1 PCB • Evaluate across 2 PCB PCB warpage metrology dimension, 2 materials thickness, 2 PCB • Metrology matching and 2 PCB fabricators dimension Focus of this presentation

DOE Set-up Objective: Evaluate the impact of the PCB fabrication process on PCB warpage DOE Factors Level 1 Level 2 PCB fabrication house Supplier A Supplier B PCB fabrication process Condition A Condition B PCB location within manufacturing panel Center Corner PCB thickness 0.6mm 0.8mm PCB material Mid Tg High Tg Post processing Yes No Fixed Factors: BGA land pattern Response Variable: PCB & local area of interest (i.e. > 35mm large BGA & Shield fence area) warpage measurements at room temp and peak reflow temperature (240 o C) Partial DOE

Summary of DOE Phase 1: Metrology matching study Phase 2: The effect of post PCB manufacturing bake on PCB warpage DOE Leg PCB Fabrication Process PCB Material PCB Thickness (mm) Post Processing 1 Condition A Mid. Tg 0.8 No 2 Condition A Mid. Tg 0.8 Yes Phase 3: The effect of PCB manufacturing, thickness, and material on PCB warpage DOE Leg PCB Fabrication Process PCB Material PCB Thickness (mm) Post Processing 3 Condition B Mid. Tg 0.8 No 5 Condition A High Tg 0.8 No 7 Condition B High Tg 0.8 No 9 Condition A Mid. Tg 0.6 No 11 Condition B Mid. Tg 0.6 No 13 Condition A High Tg 0.6 No 15 Condition B High Tg 0.6 No Note: Partial factorial DOE was performed

Summary of Press/Lamination Conditions Vendor A Vendor B Attribute Condition A Condition B Condition A Condition B Mid. Tg High Tg Mid.Tg High Tg Mid. Tg & High Tg Mid. Tg & High Tg Lamination Temp. (curing) °C >170 >190 >170 >190 170 175 1.58 (inner layer) Heating Rate (°C/min) 1.77 2.85 1.43 2.28 2.4 1.62 (outer layer) Cold Press Time (minutes) 40 40 70 70 40 70 Cure Time (minutes) 77 110 103 122 96 70

Experimental Set-up: Copper Balancing ≤ 10% Copper Balance, Solid Outrigger Copper Balance Layer Percent Layer Copper Density Percent Outrigger Copper Density 1 ≥ 95 72.9 2 ≥ 95 84.4 3 ≥ 95 89.2 4 ≥ 95 73.1 5 ≥ 95 77.9 6 ≥ 95 77.3 7 ≥ 95 74.1 8 ≥ 95 82.9 9 ≥ 95 86.1 10 ≥ 95 82.6

Experimental Set-up: Stack-ups Thin PCB: ~0.6 mm Thick PCB: ~0.8 mm thickness (um) thickness (um) S/M 15 S/M SolderMask 40 L1 1/3oz+plating 25 L1 Copper(Base+Plating) 30 prepreg PP1037 40 prepreg Prepreg/1-1067 55 L2 1/3oz+plating 15 L2 Copper(Base+Plating) 25 prepreg PP1037 40 prepreg Prepreg/1-1067 55 L3 1/3oz+plating 15 L3 Copper(Base+Plating) 25 prepreg PP1037 40 prepreg Prepreg/1-1067 55 L4 1/3oz+plating 15 L4 Copper(Base+Plating) 25 prepreg PP1037 50 prepreg Prepreg/1-1067 55 L5 1/3oz+plating 15 L5 Copper(Base+Plating) 25 Core 2.6mil 65 Core Core 60 L6 1/3oz+plating 15 L6 Copper(Base+Plating) 25 prepreg PP1037 50 prepreg Prepreg/1-1067 55 L7 1/3oz+plating 15 L7 Copper(Base+Plating) 25 prepreg PP1037 40 prepreg Prepreg/1-1067 55 L8 1/3oz+plating 15 L8 Copper(Base+Plating) 25 prepreg PP1037 40 prepreg Prepreg/1-1067 55 L9 1/3oz+plating 15 L9 Copper(Base+Plating) 25 prepreg PP1037 40 prepreg Prepreg/1-1067 55 L10 1/3oz+plating 25 L10 Copper(Base+Plating) 30 S/M 15 S/M SolderMask 40 overall board thickness 605 overall board thickness 840

Experimental Set-up: Manufacturing Panel Layout ~64 mm ~79 mm • One Manufacturing panel è Eight shipping panels • 1 Shipping panel = 4-up (i.e. 4 PCBs) • Red boxes è BGA area warpage measurement (~13 mm x 13 mm) Shipping panel location è 1,2,7,& 8 è Corner panels • • Yellow box è Panel area warpage measurement • Shipping panel location è 3-6 è Center panels

Phase 1: Matching Study

Phase 1: Matching Study 1. Step Block for Accuracy evaluation at room temperature Precision machined steel block with steps of ~25 µm, ~139 µm, & ~265 µm for linearity check in accuracy measurements was used The block was ISO certified by third party Test site C provided the step block for this matching study 2. Lens for thermal repeatability Optical flat lens from fused silica with known radius of curvature 16 measurements at Room Temp, 150 C & 250 C using J-STD-020 peak reflow temperature specification called out in IPC 9641 specification (section 5.4 and section 6) A flat surface was ensured at the edge of lens 3. Thermal performance comparison Compare thermal performance of the various tools following J-STD-020 peak reflow temperature specification PCB with thermocouples were attached and measurements were performed by external data logger Maintained a lower reflow max temp to avoid degradation

Phase 1: Matching Study 1. Step Block for Accuracy evaluation at room temperature Block Step Heights Success Criteria Site B (µm) Site C (µm) Site D (µm) Site E(µm) Step 1 (24.384 µm) ±2% (23.9 µm – 24.9 µm) or Tool Mean: 23.0 Mean: 24.2 *Mean: 21.9 *Mean: 23.6 Resolution (± 5 µm) STDEV: 0 STDEV: 0.05 STDEV: 0.62 STDEV: 0.07 Step 2 (139.192 µm) ±2% (136.4 µm – 142.0 µm) or Tool Mean: 136.3 Mean: 138.5 Mean: 139.5 Mean: 139.0 Resolution (± 5 µm) STDEV: 7.32 STDEV: 0 STDEV: 1.27 STDEV: 0 Step 3 (265.43 µm) ±2% (260.1 µm – 270.7 µm) or Tool Mean: 258.6 Mean: 264.6 Mean: 266.8 Mean: 267.0 Resolution (± 5 µm) STDEV: 0.51 STDEV: 0.05 STDEV: 0.92 STDEV: 0 *Step 1 measurements from sites D & E, small area right next to the step was ignored because it impacted the measurement All test sites, with the exception of test site B, met the ±2% target value

Phase 1: Matching Study 2. Lens for thermal repeatability Optical Lens – Manufacturer M Optical Lens – Manufacturer N Temperature (°C) Success Criteria Site B (µm) Site C (µm) Site D (µm) Site E (µm) Mean: 398.69 Mean: 381.03 Mean: 686.0 Mean: 684.94 ±5% from Target 24 STDEV: 2.57, CV = STDEV: 0.52, CV = STDEV: 0.62, CV = STDEV: 0.77, CV = 0.006 0.001 0.001 0.001 Optical Lens M Target 372.8 Mean: 398.38 Mean: 380.93 Mean: 685.0 Mean: 683.88 to 388.0um, 150 STDEV: 4.41, CV = STDEV: 0.80, CV = STDEV: 3.5, CV = STDEV: 1.63, CV = 0.011 0.002 0.005 0.002 Optical Lens N Target 671.3 Mean: 397.13 Mean: 380.93 Mean: 686.0 Mean: 682.0 to 698.7um STDEV: 1.02, CV = STDEV: 1.13, CV = STDEV: 4.4, CV = STDEV: 1.5, CV = 250 0.003 0.003 0.006 0.002 All test sites, with the exception of test site B, met the ±5% target value

Phase 1: Matching Study 3. Thermal performance comparison Delta Temperature (°C) Temperature (°C) Success Criteria (°C) Reflow Oven Site B Site C Site D Site E 24 ≤ 10 o C 0.33 0.44 2.00 0.30 1.20 150 ≤ 10 o C 6.67 17.96 7.40 6.50 4.70 200 ≤ 10 o C 4.61 15.78 7.40 4.20 4.60 Peak ++ ≤ 10 o C 3.34 12.10 6.40 4.40 4.20 Time to 220 (sec) NA 152 245 336 400 404 All test sites, with the exception of test site B, met the ≤ 10 °C technical equivalency Key Takeaway à Test sites C, D, & E were used for testing in this work